I'm considering a Nikon D3100 as it is a DSLR and therefore provides flexibility of lenses, exposure and focal configurations, shallow depth of field as well as a viewfinder, useful in bright sunlight. There is also a vanity factor in that it looks (and is to some extent) a proper DSLR camera - great for work at functions where one would need to be taken seriously rather than carrying around a silver cigarette-sized compact.

However, I've noticed that smaller, non-DSLR cameras are becoming more advanced and appear to be greatly overlapping capabilities of entry-level/prosumer DSLRs (i.e. DSLRs which are APS-C not full 35mm full frame). Their compactness is an advantage and they offer lenses that are interchangeable. Examples include those from Olympus (PEN), Samsung etc.

What should I be looking for that would tip me in either direction, apart from the saying "the best camera is the one you have with you".

4 Answers
4

Against a bridge camera or high-end compact, the arguments are straightforward: a larger sensor gives better image quality, and interchangeable lenses give more flexibility.

For dSLR vs. one of the mirrorless alternatives, it's more complicated, but there's two broad reasons here as well: technology maturity and system maturity.

Under technical maturity:

Contrast-detect autofocus as used in most compact and mirrorless cameras is just not as fast as phase-detect. This will change as processor power and algorithms improve, but phase-detect has an intrinsic advantage because the AF sensors tell the system "go this direction to get the correct focus", whereas contrast detect has to seek back and forth to see which way is better. Perhaps in the future, a hybrid solution will be preferred, or perhaps contrast-detect (which already has an accuracy advantage) will become fast enough that it just won't matter.

Electronic viewfinders have come a long way, but they still don't beat optics. This is an area that will definitely change: I'm very comfortable saying that in ten years, electronics will beat optics in every way. Five years, maybe. Right now, though, advantage to through-the-lens optics.

System maturity:

Fewer choices for lenses or for TTL-automated flashes. The systems are relatively new and being built up from scratch. You can use lens adapters in many cases, but usually with reduced functionality (and without the advantages of smaller size). If a compact mirrorless system has what you want (and they do cover the basics), this might not hold you back, but a more-established system — even including relatively small ones like 4/3rds (in the non-micro form) — offers more flexibility.

One can't help but notice that the two 800-pound gorillas, Canon and Nikon, haven't thrown their hats in the ring. (Gorillas wear hats, right?) That's not a problem, per se, but it might be a reason to keep watching.

Update: Rumor has Nikon announcing a mirrorless interchangeable lens camera Very Soon Now. This looks to be an interesting offering, because, like the Pentax Q, it uses a tiny compact-camera-sized sensor. This basically fits under all of the caveats above (except the gorilla one, of course), with the addition of the sensor size concerns. Time will tell on quality, but it looks like these will basically fall under "expensive toy designed for the Japanese market" rather than competition to dSLRs.

Thanks, so is phase-detect always used in DSLRs, is it a mandatory requirement for the camera to be called a DSLR.
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robservodavistaAug 2 '11 at 15:42

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@Rob, it's not mandatory, but it's part of the typical design. DSLRs in live-view mode use contrast detection, and there may be some fancy designs that allow that in normal mode as well.
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mattdmAug 2 '11 at 16:42

Speed: many P&S and even these newer bridge cameras take time to initialize as well as focus and take a shot. This can be frustrating when you want the shot NOW! when the action is occurring. This can be especially true when the camera is off.

DSLRs start up quickly, but more important, when you push the shutter button, the shot happens, instantly. They also shoot faster with more frames. This by and large is the one area where DSLRs are absolutely superior to nearly every other form factor.

"newer bridge cameras take time to initialize as well as focus and take a shot." is that always the case? fair enough if so. But is initalizing to do with firmware rather than an inherent disadvantage of a bridge camera? In other words, could DSLRs also have slow firmware?
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robservodavistaAug 2 '11 at 15:41

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This has been a significant difference for DSLR since, well most DSLRs. It certainly is the case with the Nikon and Canon cameras: they start instantly. More importantly, the shoot instantly. When you press the button of P&S, it will pause before shooting. If you press the button of my Canon 40D, you get 4 shots before you realize you pressed all the way down.
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cmasonAug 2 '11 at 16:38

+1 for your answer and comment. Would this instant start and quick start apply to the Nikon D3100? I guess so, but wondered...
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robservodavistaAug 3 '11 at 12:27

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I don't have any experience with that model, but I would imagine it would. You can read about its performance here: dpreview.com/reviews/nikond3100/page9.asp Note that dpreview tests start up and time-to-shoot on P&S, but do not bother with DSLR any longer, and it is not even mentioned in the Nikon D3100 review.
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cmasonAug 3 '11 at 18:35

The best thing you can do is figure out what you want out of a camera first and then searching for cameras that match that need.
It is true that the "non DSLR Cameras" are becoming more advanced but most of these features are implemented in the DSLR variants and in some degrees better.

I usually see DSLRs as giving you much more flexibility, if you just want to be able to shoot video and don't care about the settings, then the point and shoot (PnS) cameras will cover you, if you want to be able to control your frame rate and exposure settings and focus, you are better off in a DSLR in most cases.

The same goes for exposure, the canon G12 gives you full control over iso and aperture and shutter speed, it doesn't have the focus speed or low light focusing ability of its bigger DSLR brothers but if that is not a requirement then why pay for something you won't use?

Also the more compact a camera is, the more likely you are to carry it with you. Having a DSLR with interchangeable lenses and possibly an external flash will definitely give you better image quality when used right, but you might not bother to carry it out with you and then the statement you hate is true "the best camera is the one you have with you" because now your camera is useless, sitting at home in a bag collecting dust.

I find my DSLR is always giving me far superior photos to a g12 in conditions where focus speed, low light performance or depth of field control are important factors. For snapshots and basic shots, there is nothing in it.
2 examples:

When I'm shooting at a party in low light with my DSLR, my external flash has a focus assist grid that means focusing is flawless every time and lightning fast and the quality of light from that flash is undeniably superior. A G12 will use its little assist light and blink and take a number of seconds to get focus and eventually fire. The flash giving you boring on camera flash light. If i strap a proper flash to it however, the experience is about the same, it feels ridiculously unbalanced but still, you can get that same quality of light.

If i put a g12 on a tripod and do a landscape photo, I can yield basically the same image of my big hulking canon 40d when all I am doing is shooting a scene without filters and so on.

Sure. Interchangeable lens examples are Sony NEX and Samsung NX. Then there's Fujifilm X100, and also the Ricoh A12 module (and the upcoming M-mount module). And Sigma's DP1 and DP2 are on the small side but generally counted as APS-C. They're not showing up in your snapsort search because they're classified under "mirrorless" rather than "digicam". Snapsort, somewhat questionably, also puts the Leica M9 in the same category. (Technically true but an indicator that the categorization isn't the most helpful.)
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mattdmAug 8 '11 at 17:33

ahh... I wouldn't have really considered most of those "compact" since the main difference is just the existence of a mirror... They're still nearly as large as a DSLR.
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chills42♦Aug 8 '11 at 17:46

They're not exactly for going clubbing, but definitely smaller than SLRs. But particularly here, refer to the context of the question above. :)
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mattdmAug 8 '11 at 18:53